Question

_____ class did an experiment of dropping alka-seltzer tablets into water. They concluded that the mass decreases slightly when the Alka-Seltzer dissolves. Provide a better explanation for the class results and propose a method for more accurate results.

Answer 1

If the tablet is just dissolving, it's total mass hasn't changed. Rather, the individual molecules that make up the tablet have separated from one another due to interactions with the water molecules, making the tablet "disappear" only because it has split up into many parts too small to see. If the experiment was conducted on a scale, you'd see this is the case, because the mass of the water+tablet would remain the same even after the tablet dissolves.